156 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



1. HEMICARPHA 



Plants annual, dwarf, with tufted slender stems; spikelets terminal, 

 solitary or in clusters of 2 to 4, not more than 3 mm. long, terete, sub- 

 tended by 1 to 3 leaf-like bracts; flowers all perfect, subtended by 

 spirally imbricate scales; stamen 1. 



Key to the species 



1. Scales oblong or narrowly obovate, with a short recurved tip; achenes cylindric, 

 brown, with many crowded papillae. 1. H. micrantha. 



1. Scales broadly obovate or rhombic, with a blunt appressed tip; achenes nar- 

 rowly obovoid, ashy, with fewer and less crowded papillae. 



2. H. DRUMMONDII. 



1. Hemicarpha micrantha (Vahl) Pax in Engler und Prantl, Pflanzen- 



fam. 2 2 : 105. 1887. 



Scirpus micranthus Vahl, Enum. PL 2: 254. 1806. 



Cochise, Santa Cruz, and Pima Counties, 2,400 to 4,000 feet, in 

 wet sand along streams. New Hampshire to Florida, west to the 

 Pacific and southward to South America. 



2. Hemicarpha drummondii Nees in Mart, Fl. Bras. 2 1 : 62. 1842. 

 Camp Lowell, Pima County (Rothrock 715). Western Ontario to 



Indiana, Texas, and southern Arizona. 



Specimens from the foot of the Rincon Mountains, Pima County, 

 (Kearney and Peebles 10476), and from Sycamore Canyon near Ruby, 

 Santa Cruz County (Kearney and Peebles 14482), seem to be inter- 

 mediate between this species and H. micrantha. 



2. CYPERUS. Flat-sedge 



Plants annual or perennial; stems triangular; leaves mostly basal, 

 with 1 or more apical leaves forming an involucre to the inflorescence; 

 spikelets in simple or compound umbels or heads, often flat, with the 

 scales in 2 ranks ; stamens 1 to 3 ; achene lenticular or triangular, not 

 subtended by bristles. 



Most of the species inhabit marshes and banks of streams but a few 

 occur in pine woods. They flower in summer. Nutgrass (C. rotun- 

 dus) and chufa (C. esculentus) are troublesome weeds in irrigated land 

 in southern Arizona and are difficult to eradicate, because of the nut- 

 like underground tubers by which they propagate. These tubers are 

 greatly relished by pigs. 



Key to the species 



1. Achene lenticular (biconvex); style branches 2; scales obtuse, sometimes 

 mucronulate (2). 

 2. Scales loosely imbricate, broadly white-margined toward the apex; inflores- 

 cence open, not appearing lateral, more than 2 cm. long, the rays elongate. 



10. C. ALBOMARGINATUS. 



2. Scales closely imbricate; inflorescence dense, subcapitate, not more than 2 

 cm. long, the rays almost none (3). 

 3. Spikelets rather turgid; scales less than 2 mm. long, thin, whitish, often 

 blotched with liver color; flowering stems from slender, creeping root- 

 stocks; inflorescence appearing lateral, the longest bract of the invo- 

 lucre erect and resembling a continuation of the stern. 



8. C. LAEVIGATTJS. 



3. Spikelets flat; scales 2 mm. long or longer, light brown or chestnut-colored; 

 flowering stems from creeping rootstocks, or cespitose and the plant 

 appearing annual; inflorescence usually not appearing lateral, the bracts 

 more or less spreading 9. C. niger. 



